114 research outputs found
Helical states of nonlocally interacting molecules and their linear stability: geometric approach
The equations for strands of rigid charge configurations interacting
nonlocally are formulated on the special Euclidean group, SE(3), which
naturally generates helical conformations. Helical stationary shapes are found
by minimizing the energy for rigid charge configurations positioned along an
infinitely long molecule with charges that are off-axis. The classical energy
landscape for such a molecule is complex with a large number of energy minima,
even when limited to helical shapes. The question of linear stability and
selection of stationary shapes is studied using an SE(3) method that naturally
accounts for the helical geometry. We investigate the linear stability of a
general helical polymer that possesses torque-inducing non-local
self-interactions and find the exact dispersion relation for the stability of
the helical shapes with an arbitrary interaction potential. We explicitly
determine the linearization operators and compute the numerical stability for
the particular example of a linear polymer comprising a flexible rod with a
repeated configuration of two equal and opposite off-axis charges, thereby
showing that even in this simple case the non-local terms can induce
instability that leads to the rod assuming helical shapes.Comment: 34 pages, 9 figure
Cities in fiction: Perambulations with John Berger
This paper explores selected novels by John Berger in which cities play a central role. These cities are places, partially real and partially imagined, where memory, hope, and despair intersect. My reading of the novels enables me to trace important themes in recent discourses on the nature of contemporary capitalism, including notions of resistance and universality. I also show how Berger?s work points to a writing that can break free from the curious capacity of capitalism to absorb and feed of its critique
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